A kinetic method employing single substrates (warfarin and phenprocoumon) and multiple product ratios will be utilized to probe crude microsomal enzymatic mixtures in order to obtain information on how many enzymes are present in the mixture. Quantitative changes produced in product profiles as a function of perturbations to the system by the use of enantiomeric substrates, various inducers and inhibitors should allow the determination of the specific catalytic properties of individual enzymes. Such information will not only be useful in correlating results obtained from purified enzymatic systems but will increase our understanding of the catalytic nature of these enzymes and suggest ways in which chemically induced toxicities caused by the generation of reactive intermediates in the process of biotransformation can be circumvented.